Project Summary: Individual physician decision-making is an important determinant of the extent of variation in health care practice in the U.S. The emergency department (ED) presents an ideal setting for studying the determinants of variation in decision-making. Knowing the fundamental importance of risk aversion in lay decision-making, we hypothesize that risk aversion has the potential for an even stronger influence on emergency physicians (EPs) because of the high stakes and uncertain nature of emergency care. This study will focus on risk aversion and Need for Cognitive Closure (NFC), related traits that might have a profound impact on decision-making in the ED. Together, these traits translate into a certain level of clinical anxiety or compulsiveness amongst EPs. The distribution of this trait amongst EPs is unclear, as is whether this personality trait is beneficial or harmful for patients. It is likely that a particularly anxious or compulsive EP will be vulnerable to over-testing (errors of commission), and that this over-testing results in potentially harmful downstream outcomes. Yet, in the ED setting it is possible that for some clinical conditions, over-testing in the ED setting might be protective by minimizing missed diagnoses and picking up on potentially critical diagnoses. It simply is unknown and critical to define for most ED conditions whether higher or lower testing is better, or if a range of testing is associated with better outcomes. A critical need exists to determine whether these traits are associated with the intensity of workups and admission decisions in the ED. Delineating this relationship is essential to devising interventions to educate EPs about their intrinsic risk aversion or to set expectations of an ideal level of practice intensity for key clinical conditions. Yet, even the prevalence of risk aversion and NFC amongst EPs ? and the relationship between them and decision-making ? is largely unknown. The proposed study will combine survey data from EPs ? as well as from Advanced Practice Providers given their increasing role in the provision of emergency care- across Massachusetts with utilization data from an all payer claims database (which we will construct by combining Medicare claims data and the Massachusetts All Payer Claims Database) to accomplish three key aims. First we will measure the prevalence and distribution of risk aversion and NFC in the population of Massachusetts EPs/APPs. We will then determine the relationship between provider risk aversion/NFC scores and practice intensity (the number of laboratory tests, imaging studies, and the frequency of hospital admission) for key clinical conditions in the ED. Finally, we will examine the relationship between practice intensity and patient harm, leveraging the fact that patients are randomly assigned to EPs. In addition to shedding light on a largely unexplored area of medical decision-making, our findings will serve as the foundation for the development and implementation of behavioral interventions aimed at guiding providers with different levels of risk tolerance to more standard management decisions or to managing the interface between risk aversion and the cognitive bias that may result.